Asymmetric cryptography, or public-key cryptography, is the foundation of security protocols that do not require shared secrets.

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Brute force symmetric knowing asymmetric

Lets say message A is encrypted with symmetric encryption. BUT before encrypting the message, it is asymmetrically encrypted (let's say to implement VPN ...). Now if a man in the middle captures the ...
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How is the private key kept secret in digital signatures?

A digital signature is verified using an algorithm that takes three inputs: the message, the digital signature (message encrypted with private key)* and the public key. If the public key is used to ...
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2answers
51 views

Asymmetric key encryption that can have a public decryption key, but encryption key cannot be computed from that [duplicate]

Is there a way where I can distribute a public decryption key, but the encryption key cannot be computed from that key, so that anyone who reads one of my encrypted message, he/she can be quite sure ...
3
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2answers
916 views

How to securely store sensitive data on mobile application?

I want to develop a mobile bank app (Windows Phone, Android, iOS) that interact with a bank channel. First time when user opens application the key exchange process begins and at end of this process ...
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1answer
87 views

Reducing asymmetric authorization token size

I would like to use an asymmetric rather than symmetric signature for authorization, since I don't want a compromised service being able to forge authorization tokens (obviously). An authorization ...
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2answers
85 views

Suggestion on asymmetric (hybrid encryption) encryption for big file

We will be using following commands to encrypt to firmware file at server and that will be decrypted on the embedded board using decryption command mentioned below, Following command will be used to ...
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27 views

ISO 9564 Approved Encryption Algorithms for PIN, why symmetric block ciphers?

I am currently researching best practices in designing a potential PIN management solution for a financial services application and began looking into ISO 9564 as a source of requirements. One of the ...
4
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1answer
88 views

Ways to generate symmetric and asymmetric keys

We are using Beaglebone Black based custom board, and want to use hybrid encryption for encrypting firmware file, i.e. symmetric for encryption big firmware file and asymmetric for encrypting ...
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2answers
58 views

How does digital signature algorithms work in a private / public key environment?

From the Wikipedia page on the subject, I get, on a theoretical level, how the process of encrypting and decripting a message works. The article states that: In a public-key encryption system, any ...
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1answer
89 views

Public Key Encryption vs HSM for storing encryption keys

Let's say I have sensitive data in the database server that needs to be encrypted (i.e emails, etc..) and I want to make sure that in the event that the server is compromised, the attacker shouldn't ...
2
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1answer
237 views

SQL Server Asymmetric Encryption Keys

I have used SQL Server database with data to be encrypted and I will use symmetric key for encryption and will encrypt it by asymmetric key now comes the question how to give user permission to ...
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1answer
101 views

Preventing someone to generate a public key from a private one? [closed]

From what I read, encryption algorithms such as RSA permits to generate the public key from the private one. Long story short, for a thesis I'm writing, I thought to solve a security issue with users ...
2
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1answer
48 views

Way to combine encrypted tar and encrypted symmetric key with which tar was encrypted?

We are using Beaglebone Black (AM335x) based custom board, so for firmware upgrades of the board we will be using an encrypted firmware image. As you would have already guessed, we will be using ...
5
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3answers
5k views

Shared Secret, is it a public key or a private key?

Reading the Diffie-Hellman non mathematical explanation i found that some mathematical operations are performed on private-key and the recipient's public key to generate a "shared secret" on both ends ...
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0answers
32 views

Use MDC to provide origin authentication for public key encryption?

Why can't we use an manipultation detection code (MDC) to provide origin authentication when using public-key encryption?
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2answers
67 views

Asymmetric Encryption for Multiple Recipients?

Let's assume an arbitrary group of people who hold a key pair and who make their public key online accessible. Let X, A, B and C be arbitrary people from that group. Now X wants to encrypt a message ...
3
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0answers
79 views

Security of the shared secret key for a smart meter (Linky) [closed]

Reading the specs of a new electricity smart meter (called Linky in France), I was surprised about the chosen encryption method (128 bits symmetric key AES), based on a single secret key (called CCC ...
0
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1answer
112 views

Why doesn't my manual RSA key exchange example work?

I'm trying to "manually" compute how the premaster_secret is computed using the RSA key exchange in TLS 1.2, but can't manage to make numbers meet. I am using Scapy SSL to generate a TLS session: I ...
2
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1answer
116 views

What is the difference between a digital signature and whole message encryption?

I am newbie in information security I am trying to understand the difference between a digital signature and encryption of a message. Lets consider simple example of email message. I understand how ...
0
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1answer
103 views

How to verify the signature value in a SSL certificate?

According to RFC 3280 a certificate's basic syntax is Sequence := { tbsCertificate signatureAlgorithm signatureValue } In tbsCertificate, SubjectPublicKey is the public key of the ...
7
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3answers
1k views

What are the disadvantages of using public key cryptography when encrypting files? [duplicate]

I am wanting to encrypt a file with my public key, my friend told me that this is not a good idea but did not explain why. Can someone explain please.
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5answers
205 views

Secure application data transmission via SMS channel

There are mobile banking applications that use SMS channel to communicate with their server. Some of them offer both internet and sms channels which the customer gets to choose from. While there's ...
2
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1answer
48 views

What does it mean to sign a public key and what's wrong with signing someone else's key?

I just stumbled upon this comic and I'm not sure if I understand what's going on. I googled and I figured that somehow people can sign other people's public keys and then they that person is genuine. ...
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0answers
75 views

For multiple clients it's better symmetric or assymetric encryption?

I'm a newbie in the encryption world so I'm here for asking which is the best solution between Symmetric and Asymmetric encryption. In our use cases, we have multiple clients that must be ...
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1answer
67 views

how is public key being exchanged in asymmetric cryptography?

I understand that exchanging public key between parties is challenging task in asymmetric cryptography.Can someone help me understand how it is achieved?
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2answers
101 views

How are private and public keys different?

While reading about DKIM I saw that the sender's private key is used to encrypt a hash, later decrypted by the recipient using the sender's public key. This is exactly the other way compared to ...
113
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6answers
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“Diffie-Hellman Key Exchange” in plain English

Can someone explain to me what Diffie-Hellman Key Exchange is in plain English? I have read in a non-tech news page that Twitter has just implemented this technology which allows two persons to ...
6
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1answer
2k views

How secure is GPG symmetric encryption?

Since I am new to encryption and have recently been losing stuff, I decided to start a file that contains some passwords for online accounts and whatnot, encrypt it, back it up (and keep a single copy ...
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2answers
110 views

Password based Asymmetric Key generation

I am looking for a password based key derivation scheme that results in an asymmetric key pair. I have worked with PBKDF and its variants but could not come up with any way of generating a key pair. I ...
11
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1answer
381 views

Recommended operational security for generating one's primary key pair?

I have been looking for an operational security guide for generating one's asymmetric key pair for (Open)PGP. I have found plenty of technical guides for how to use GnuPG to generate RSA key-pairs, ...
0
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1answer
63 views

How to make a good choice between Symmetric and Asymmetric [closed]

Here and there and read a lot of articles and blog posts titled "Difference Between Symmetric Cryptography and Asymmetric Cryptography". But inside of them they are answered "What is Symmetric ...
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1answer
83 views

What happens if two parties have the same public key? [closed]

What would happen if I get a public key that someone else already has? Isn't the security very weak in that case?
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5answers
150 views

Is it secure to ship public key with license file?

I've implemented a licensing client and server for our web-applications. Currently there is only one way for licensing an app, user should manually upload the license file using specified form and ...
5
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3answers
176 views

Public Key Encryption instead of passwords

As an alternative to using passwords, customers could be provided with individual asymmetric-encryption key pairs (i.e. a private key with associated public key), which could be used to validate their ...
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0answers
53 views

stream cipher & e-banking

As I read on internet, I ran into these two question. Yet, I thought about it but still don’t know how to tackle it. May I have your help? (a) During an e-banking transfer the bank uses a stream ...
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Encrypt data within mobile app and send to web service

I'm developing a mobile application for Android and iOs. What is best practice when it comes to data encryption within the mobile application which will be sent to a web service? Basically I will ...
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1answer
56 views

ssl - How is asymetric algorithm used in SSL/TLS?

Okay I have read the questions here on how SSL works, but they all focus on symmetric encryption. But I have configured Apache WebServer to use RSA for SSL using the openSSL tool. Now my question is ...
8
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2answers
867 views

ProtonMail security concerns

This TED talk brought me here. First of all, to those who created ProtonMail: Nice job!!. Regardless of what people say, it's definitely a big step forward from tradition options like Hotmail, Gmail ...
43
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4answers
5k views

Why is key exchange necessary at all?

Let's say "Alice" and "Bob" want to communicate with each other over an insecure network. Using Diffie–Hellman key exchange, they can get the same symmetric key at last. However, as I understand, ...
2
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1answer
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Use asymmetric encryption once to exchange symmetric key

I'm developing a json API that should be able to handle a huge amount of clients. To make this work I need to reduce the overhead as far as possible. One of the ideas I have is to use https only in ...
2
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2answers
2k views

Does public key auth in SSH prevent most MITM attacks?

I found this article that claims asymmetric crypto signature of DH-obtained key prevents MITM: http://www.gremwell.com/ssh-mitm-public-key-authentication Key idea: The value of 'signature' is a ...
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3answers
147 views

In message signing, is the digest encrypted with a generated symmetric key or with the sender's private key?

I understand the encryption process uses a generated symmetric key to encrypt a message, and then encrypts the symmetric key with the receiver's public key before it is sent across the wire. This ...
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0answers
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Purpose of MAC when encrypting? [duplicate]

Really basic question, but what is the purpose of using a MAC/HMAC when you are encrypting using a symmetric key algorithm? It is my understanding that the purpose of a MAC is to authenticate the ...
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0answers
62 views

Curve25519xsalsa20poly1305 key derivation

I'm working on batch-encryption of files, for a small project of mine. The files are stored encrypted on a removable drive, and the keys are stored on a trustful server. For enhanced safety, I'd like ...
0
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1answer
83 views

In Asymmetric cryptography, is the number of Private Keys limited?

My question is a bit of a leading question, because I assume that the number of Private Keys is a finite number. However, it is possible that the number is such a large number that it would ...
1
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1answer
69 views

Need asymmetric encryption(not signing) where server encrypts and client decrypts

So I'm trying to build a licensing server, where the licenses of the applications need to be checked when logging in or when the application gets used. But some of those application work offline most ...
1
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2answers
214 views

Difference between KMS and PKI

While the PKI System deal with digital certificates life cycle and Key Management System (KMS) deal with keys life cycle. What is the the fundamental difference between them? Is it possible to ...
0
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1answer
314 views

RSA: same symbols in plaintext give same symbols ciphertext?

I just started studying Information Security, but I just ran this program: http://www.sanfoundry.com/cpp-program-implement-rsa-algorithm/ and faced this strange thing. For small keys (don't try to ...
3
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2answers
223 views

Why can I sign but not encrypt?

-edit- After following a chain of links from this question I see this is similar/duplicate of Why should one not use the same asymmetric key for encryption as they do for signing? but this question ...
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Cloud-based IM protocols / services saving messages encrypted on server which is decryptable only by user? [closed]

I am looking for a cloud-based (i.e. not end-to-end) secure IM protocol or service. The first one comes to my mind is telegram. Here is a quote from telegram's privacy policy: Cloud Chats ...